Java递归和非递归二分查找

非递归实现二分查找

/**
	 * 非递归查找key
	 * @param array
	 * @param key
	 * @return
	 */
	public static int binarySearch(int[] array, int key) {
		bubbleSort(array);
		int left = 0;
		int right = array.length - 1;
		int mid;
		while (left <= right) {
			mid = (left + right) / 2;
			if (array[mid] == key) {
				return mid + 1;
			} else if (array[mid] < key) {
				left = mid + 1;
			} else {
				right = mid - 1;
			}
		}
		return -1;
	}

递归实现二分查找

/**
	 * 递归查找key
	 * 
	 * @param array
	 * @param key
	 * @param left
	 * @param right
	 * @return
	 */
	public static int sort(int[] array, int key, int left, int right) {
		if (left <= right) {
			int mid = left + right;
			if (key == array[mid]) {
				return mid + 1;
			} else if (key < array[mid]) {
				return sort(array, key, left, mid - 1);
			} else {
				return sort(array, key, mid + 1, right);
			}

		}
		return -1;
	}

查询第一个出现元素的位置

/**
	 * 查询第一个元素出现的位置
	 * 
	 * @param array
	 * @param key
	 * @return
	 */
	public static int biSearchFirst(int[] array, int key) {
		int len = array.length;
		int left = 0;
		int right = len - 1;
		int mid = 0;
		while (left < right) {
			mid = (left + right) >> 1;
			if (array[mid] < key) {
				left = mid + 1;
			} else {
				right = mid;
			}
		}
		if (array[left] != key) {
			return -1;
		} else {
			return left;
		}
	}

查询最后一个出现元素的位置

/**
	 * 查询元素最后一次出现的位置
	 * 
	 * @param array
	 * @param key
	 * @return
	 */
	public static int biSearchLast(int[] array, int key) {
		int len = array.length;
		int left = 0;
		int right = len - 1;
		int mid = 0;
		while (left < right) {
			mid = (left + right + 1) >> 1;
			if (array[mid] <= key) {
				left = mid;
			} else {
				right = mid - 1;
			}
		}
		if (array[left] != key) {
			return -1;
		} else {
			return right;
		}
	}